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transform: coerce empty strings to NULL when converting TEXT columns to numeric types (#805)

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* transform: coerce empty strings to NULL when converting TEXT columns to numeric types

When a TEXT column is transformed to INTEGER, FLOAT, or REAL and a row
contains an empty string, the empty string is now converted to NULL during
the INSERT...SELECT copy, matching the expected behavior described in #488.

Fixes #488
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ikatyal2110 2026-08-13 14:56:51 -05:00 • committed by GitHub
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5 changed files with 57 additions and 5 deletions
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36
tests/test_transform.py
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@ -27,7 +27,7 @@ from sqlite_utils.utils import OperationalError
{"types": {"age": int}},
[
'CREATE TABLE "dogs_new_suffix" (\n "id" INTEGER PRIMARY KEY,\n "name" TEXT,\n "age" INTEGER\n);',
'INSERT INTO "dogs_new_suffix" ("rowid", "id", "name", "age")\n SELECT "rowid", "id", "name", "age" FROM "dogs";',
'INSERT INTO "dogs_new_suffix" ("rowid", "id", "name", "age")\n SELECT "rowid", "id", "name", NULLIF("age", \'\') FROM "dogs";',
'DROP TABLE "dogs";',
"PRAGMA legacy_alter_table=ON;",
'ALTER TABLE "dogs_new_suffix" RENAME TO "dogs";',
@ -63,7 +63,7 @@ from sqlite_utils.utils import OperationalError
{"types": {"age": int}, "rename": {"age": "dog_age"}},
[
'CREATE TABLE "dogs_new_suffix" (\n "id" INTEGER PRIMARY KEY,\n "name" TEXT,\n "dog_age" INTEGER\n);',
'INSERT INTO "dogs_new_suffix" ("rowid", "id", "name", "dog_age")\n SELECT "rowid", "id", "name", "age" FROM "dogs";',
'INSERT INTO "dogs_new_suffix" ("rowid", "id", "name", "dog_age")\n SELECT "rowid", "id", "name", NULLIF("age", \'\') FROM "dogs";',
'DROP TABLE "dogs";',
"PRAGMA legacy_alter_table=ON;",
'ALTER TABLE "dogs_new_suffix" RENAME TO "dogs";',
@ -168,7 +168,7 @@ def test_transform_sql_table_with_primary_key(
{"types": {"age": int}},
[
'CREATE TABLE "dogs_new_suffix" (\n "id" INTEGER,\n "name" TEXT,\n "age" INTEGER\n);',
'INSERT INTO "dogs_new_suffix" ("rowid", "id", "name", "age")\n SELECT "rowid", "id", "name", "age" FROM "dogs";',
'INSERT INTO "dogs_new_suffix" ("rowid", "id", "name", "age")\n SELECT "rowid", "id", "name", NULLIF("age", \'\') FROM "dogs";',
'DROP TABLE "dogs";',
"PRAGMA legacy_alter_table=ON;",
'ALTER TABLE "dogs_new_suffix" RENAME TO "dogs";',
@ -1125,6 +1125,36 @@ def test_transform_preserves_autoincrement_and_sequence(fresh_db):
]
@pytest.mark.parametrize(
"new_type,expected_value,expected_type",
[
(int, 42, int),
(float, 42.0, float),
("integer", 42, int),
("float", 42.0, float),
("REAL", 42.0, float),
],
)
def test_transform_empty_string_to_null_for_numeric_types(
fresh_db, new_type, expected_value, expected_type
):
fresh_db["test"].insert_all(
[
{"id": 1, "value": "42"},
{"id": 2, "value": ""},
{"id": 3, "value": None},
{"id": 4, "value": " "},
]
)
fresh_db["test"].transform(types={"value": new_type})
rows = {r["id"]: r["value"] for r in fresh_db["test"].rows}
assert rows[1] == expected_value
assert type(rows[1]) is expected_type
assert rows[2] is None
assert rows[3] is None
assert rows[4] == " "
def test_transform_preserves_view(fresh_db):
# https://github.com/simonw/sqlite-utils/issues/831
dogs = fresh_db.table("dogs")